EXIF editor

Have you tried EXIFTool? Be sure to get a version with the GUI.  I have never tried adding in a lens ID but if it works then EXIFTool can do batch processing to change all your files at once.

http://www.sno.phy.queensu.ca/~phil/exiftool/

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Living and loving it in Bangkok, Thailand. Canon 7D - See the gear list for the rest.